Three family members in Eureka, Calif. were swept away by the ocean’s swells after plunging into the water to chase after their family dog to save it from a watery fate last month. Now, San Diego lifeguards are using that case as a prime example of the caution they are issuing to local beach-loving dog owners who could face similar dangers along the Peninsula’s shorelines during these winter months.

Ed Harris, a lifeguard sergeant and union spokesperson, said December’s vast tidal swings can make for potentially treacherous days along San Diego’s beaches in the winter.

“In November and December we get large tidal flows,” said Harris. “There are several days with a six-foot change in the tide. [This] Dec. 13, we have a high tide of 7.7 feet at 7:31 a.m. that drops down 9.6 feet to a -1.9 at 3:25 in the afternoon. Tides are complicated. Generally, we have two high tides and two low tides per day, but not always.”

These rapidly fluctuating tidal changes can lead to especially strong undertows at the confluence of the San Diego River and Dog Beach in Ocean Beach, he said.

“The San Diego River backs up with those tides and you get an enormous amount of water backing up,” he said. “The river is raised all the way back when the tide turns and starts flowing out, so it creates strong, strong currents along the jetty there at Dog Beach.”

Harris said the case of the Eureka family trying to save its dog from the ocean’s unforgiving currents is also not an uncommon sight at local beaches.

“We routinely rescue dogs and their owners at Dog Beach during these tides,” he said. “When the tide turns, the current is extremely strong. People unknowingly throw balls out and watch their dogs get swept out.”

Typically, when dog owners enter the same dangerous waters as their beloved pets, they, too, find themselves in danger, fighting for their own lives amid harsh currents that push and pull them as if they were ragdolls. Although it may be heartwrenching to watch a furry family member struggling against the current, Harris said dogs are more likely to return safely ashore than are humans.

“Dogs go at one pace and they don’t panic. That’s what kills most people in the water is panic. They’re also more resilient to the cold and have natural instincts that guide them,” Harris said, likening a dog’s instincts in ocean currents to deer crossing rivers at a 45-degree ferry angle.

Some beaches, like Sunset Cliffs, are neither under constant surveillance nor easily accessible by San Diego lifeguards. Harris urges caution to those who frequent San Diego’s beaches in the wintertime, since lifeguards may not be able to see them in the water.

“It’s very difficult for a lifeguard on duty who is watching all of Ocean Beach to pick out a head, which is all they can see,” said Harris. “From the tower in Ocean Beach, you can’t see most of the riverbank, so if a dog or a human is in the river and getting pulled out by the current, because of the bank and the slope of the beach in the distance, we can’t see them until they get into the ocean, and with the backdrop of the dark jetty, it is difficult to spot a lone head of a person or a dog.”

Harris urges beachgoers to be aware of their surroundings, remain vigilant and call officials quickly if it appears that someone has been swept out by the tide.

“If you see something at Dog Beach or Sunset Cliffs, call 911 quickly,” he said. “Don’t assume that we’re seeing it because it’s difficult for us.”